Fire resistant polychloroprene adhesive

ABSTRACT

A novel self-curing polychloroprene base adhesive composition is provided which exhibits unexpectedly superior resistance to fire and high temperature conditions, shows reduced staining properties, exhibits good shelf life and is especially useful in the building construction field in lieu of traditional fasteners such as nails, screws and the like. The composition contains polychloroprene elastomer, asbestos, a combination of heat advancing oil soluble phenolic resins, non-staining antioxidants and fillers. The novel properties of this composition are achieved by a process which includes forming a solvent solution of the phenolic resin which is admixed with magnesium or cadmium oxide. This mixture is held for a period of time for prereaction, preferably at least two weeks, or more, although shorter times will suffice. A separate admixture of neoprene, magnesium or cadmium oxide, zinc oxide, antioxidants and asbestos is formed and is thoroughly admixed in the dry state below 140*F. The two admixtures are blended for a period of about eight hours or more to provide a high viscosity composition and solvents are added to the mixed composition to reduce the viscosity to from about 23,000 to about 90,000 centipoises.

United States Patent 1191 Perkins Oct. 22, 1974 1 1 FIRE RESISTANT POLYCI-ILOROPRENE ADHESIVE [75] Inventor: Garry R. Perkins, Palatine, 111.

[73] Assignee: Spotnails, Inc., Rolling Meadows,

[22] Filed: May 7, 1973 [21] Appl. No.: 358,201

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 197,949, Nov. 11,

[52] US. Cl. 260/38, 260/328 A, 260/457 S,

Primary Examiner-Morris Liebman Assistant Examiner-S. M. Person Attorney, Agent, or Firm-Neuman, Williams, Anderson & Olson [57] I ABSTRACT A novel self-curing polychloroprene base adhesive composition is provided which exhibits unexpectedly superior resistance to fire and high temperature conditions, shows reduced staining properties, exhibits good shelf life and is especially useful in the building construction field in lieu of traditional fasteners such as nails, screws and the like. The composition contains polychloroprene elastomer, asbestos, a combination of heat advancing oil soluble phenolic resins, nonstaining antioxidants and fillers. The novel properties of this composition are achieved by a process which includes forming a solvent solution of the phenolic resin which is admixed with magnesium or cadmium oxide. This mixture is held for a period of time for pre-reaction, preferably at least two weeks, or more, although shorter times will suffice. A separate admixture of neoprene, magnesium or cadmium oxide, zinc oxide, antioxidants and asbestos is formed and is thoroughly admixed in the dry state below 140F. The two admixtures are blended for a period of about eight hours or more to provide a high viscosity composition and solvents are added to the mixed composition to reduce the viscosity to from about 23,000 to about 90,000 centipoises.

9 Claims, No Drawings CROSS REFERENCE TO RELATED APPLICATIONS This application is a Continuation-in-Part of application Ser. No. 197,949, filed Nov. 1 1, I971.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fire resistant neoprene based adhesives and cements which exhibit low staining characteristics, self-curing, good wet bonding to wood and extended shelf life.

2. Description of the Prior Art Polychloroprene based adhesives and cements which display heat curing characteristics are not new to the art. Such adhesives, for example, are disclosed in Thompson, US. Pat. No. 2,610,910 and Clawson, et al., US. Pat. No. 2,918,440. The Thompson patent discloses a neoprene based adhesive which is self-curing at room temperature or on the application of heat. These adhesives, however, show substantial staining liability and, moreover, do not pass the Forest Product Laboratories of the US. Department of Agriculture fire tests and do not show good adhesion and bonding properties to wet or frozen surfaces, which are'frequently encountered in building construction work. These compositions furthermore do not have the extreme weather resistance required for construction which is exposed to the elements. It is also noted that the prior art frequently requires the introduction of water which frequently results in additional staining hazards and contributes to poor bonding to wet or frozen surfaces at low temperatures.

SUMMARY OF THE INVENTION The present invention relates to neoprene adhesive compositions which contain a polychloroprene elastomer, asbestos, heat advancing oil soluble phenolic resins, a combination of antioxidants comprising dialkyl thiodipropionates and nickel dibutyl dithiocarbamate, magnesium oxide or cadmium oxide, and zinc oxide suspended in an appropriate solvent.

The composition described above may contain on a percentage basis from as low as 20 percent to as much as 80 percent polychloroprene elastomer, preferably from about 45 percent to 65 percent of said polychloroprene elastomer. It should be understood that polychloroprene refers to products sold as neoprene type materials, especially soft grain neoprene sold by the DuPont Corporation as AD or AC neoprenes. It should also be understood that the percentages given, unless otherwise indicated, are on a dry solids weight percent basis.

In these compositions, the phenolic resin employed may be a single fast-acting resin, but preferably is a combination of fast and slow acting phenolic resins which are frequently described as heat'advancing and oil soluble. These resins are customarily formed by polymerization of parasubstituted phenols and formaldehyde. Generally, the phenols described as resin starting materials in the Thompson patent are suitable for this purpose. The so-called fast acting or fast curing phenolic resins may be further characterizedv by their thermal stability in the adhesive. Thus, for example, the fastest acting types are stable at 500F. and above. This 2 may be exemplified by Schenectady Chemical Co. phenolic resin SPl74.

Intermediate'and slow acting or curing phenolic resins are those having thermal stability at temperatures up to 400F. are exemplified by Schenectady Chemical Co. SP-154, stable to about 380400F. and SP-l34, stable to about 300350F. Another typical slow acting or curing resin is Bakelite CKR-l634 madeby Union Carbide Co. and has thermal stability up to about 350F. The phenolic resin is incorporated in the admixture in amounts ranging from about 15 to 50 percent, preferably from about 20 to 35 percent. Phenolics incorporated are as indicated, fast acting or fast curing materials, or may be a combination of fast acting or fast curing materials with slower curing phenolics, but generally the fast curing should be present as at least 20 percent by weight of the phenolic resin component, preferably 30 to percent thereof.

The asbestos is employed in amounts ranging from 1 to 50 percent of said composition, preferably from 1 to 10 percent by weight. The cadmium oxide or magnesium oxide or mixtures thereof is employed in these compositions in amounts of from 2 to 20 percent, preferably from 2 to 10 percent. Cadmium oxide provides enhanced heat resistance in the final adhesive compositions.

Zinc oxide is incorporated in amounts of from I to 15 percent, from 1 to 10 percent by weight.

Fillers may be employed in these compositions in amounts from 0 to 50 percent by weight thereof and may include calcium silicates (hydrated or otherwise) fiberglass chop, powdered glass, clays such as Bentonite and Montmorillonite, aluminate silicate, ash, talc,

carbon black, calcium carbonate and magnesium carbonate. These fillers may be incorporated either as extenders or reinforcing-agents. Generally, the addition of fillers will provide increased shear resistance or resistance to creep of the applied adhesive.

The antioxidants dialkyl thiodipropionate and nickel dibutyl dithiocarbamate employed in combination appear to provide a dual function of preventing staining, deterioration of the adhesive, premature curing and eliminating solvent separation from the final combination. The use of these antioxidants reduces the phasing (premature curing) customarily found in neoprene cements and adhesives. The thiodipropionate antioxidants have the formula:

wherein R, and R are alkyl or isoalkyl radicals of from 9 to 20 carbon atoms. The most preferred is dilauryl thiodipropionate. The dialkyl thiodipropionate and nickel dibutyl dithiocarbamate antioxidants are generally employed in equal amounts and each may be employed in amounts of 0.1 to 2 percent by weight, although most preferably they are each employed at about 0.5 percent by weight.

The novel process employed in preparing the composition of the present invention contributes to the attainmentof the unusual physical properties exhibited by the adhesive or cement described above. Generally, the process may be described as a three-step procedure involving the following:

STEP A:

Phenolic resin is blended with an organic solvent and a a portion of the magnesium or cadmium oxide. Approximately one-half of the magnesium or cadmium oxide is employed in forming the composition of Step A. The degree of agitation is such as to provide full dispersion of the solid components. To permit adequate pre-reaction, periods of time of from at least 2 to 6 hours are necessary but pref- .erably extended periods of reaction such as about 2 weeks give the best and most uniform results. STEPB:

The neoprene (polychloroprene) elastomer is blended with the remainder of the magnesium or cadmium oxide, antioxidants, fillers and asbestos in conventional high shear rubber mixing equipment (such as a mill or Banbury) followed by dissolution of the solid admixture in an organic solvent or solvent composition.

STEP C:

The products obtained from Steps A and B are blended together in a mixe'r'and zinc oxide is then added. If desired, all or a part of the zinc oxide can be added in Step B to reduce scorch. The compositions A and B are thoroughly mixed at a temperature below about 140F., preferablybelow about 120F. for a period of at least about 2 hours but for most uniform product and best bond, preferably about 8 hours. The high viscosity mixture is then reducedin viscosity by the further addition of solvents to produce a'material having a viscosity of from 23,000 to about 90,000 centipoises and then placed into containers. For the traditional cartridge type container such as are ordinarily employed in caulking gun-type devices which are suitable for applying a predeterminedstrip or bead of adhesive, viscosities should be between about 48,000 to about 70,000. For carpet adhesives, the viscosity may run as low as about23,000 up to about 35,000

to 48,000 centipoises. This could also be used to cement a vinyl top to a car. A paste type cement suitable for troweling can have viscosities up to 90,000 centipoises.

If desired, very rapid cures may be obtained bythe incorporation of accelerators such as NA 101 which provides a rapid cure at 150 to 200F. but only at these elevated temperatures, thereby avoiding premature curing during storage. These temperatures would be encountered in roof deck installations.

The solvents which are employed in the present compositions are generally aromatic and ketone solvents such as toluene, xylene, methylethylketone and and acetone. Hexane and other aliphatics may also be used.

' The various properties of these solvents may be adsitions are also extremely resistant to high temperature conditions and fire, being able to pass the US. Department of Agriculture, Forest Product Laboratories fire test which requires the ability to withstand direct flame impingement on an exterior plywood member that is adhesively bonded to a wood structure without reduc- 'bomb aging.

A further important object is the provision of an adhesive composition which shows outstanding bonding to wet and frozen surfaces.

A still-further object is the provision of highly heat resistant fire proof mastics at relatively low cost,

A still further object is the provision of an adhesive mastic composition which has good storage stability characteristics when stored or shipped under high temperature conditions such as warehouses, trucks, boxcars and the like. I

A still further object is the provision of high performance adhesive compositions which do not require the addition of water to achieve good curing properties.

A still further object is the provision of adhesive compositions which are non-thixotropic and are readily applied at low temperatures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following specific examples will illustrate compositions prepared in accordance with procedures of the present invention:

EXAMPLE I An adhesive was prepared employing polychloroprene, phenolic resins, asbestos, antioxidants and fillers having the following composition in the weight percent portions listed below:

The foregoing materials are mixed in the following sequence procedure. STEP A:

The phenolic resins are combined and mixed with an equal amount of hexane followed by addition of one-half of the magnesium oxide (or cadmium oxide, it employed). The composition is agitated for a period of 4 to 6 hours to assure full dispersal of the solid components. The admixture is preferably permitted to pre-react for an additional period of up to 2 weeks or more for best results.

STEP B:

The neoprene elastomer is dry milled for a period of 5 minutes on a rubber mill, after which period the remainder of the magnesium and the amt-oxidants are blended in, followed by another one or 2 minutes of mixing. Further additions of hydrated calcium silicate and asbestos are made to the mixture 5 6 followed by further milling or mixing fora period The final composition was reduced to a viscosity of of from about 10 minutes to assure complete disaboutcentipoises using the Same solvent blend.

persion. In this Speciifc embodiment a Banbury was employed. The rubber or neoprene material is then diced and reduced with toluene until the mixture is 5 f m I smooth. The accelerator is then added to the sol- An adhesive composition was prepared following the vent-reduced elastomer and blended for a period of procedure of Example I employing the following com- 1 hour. The zinc oxide is also added at this time, alponents the Indicated P OP UOHSI though it can be added to the rubber in the milling P- Parts or X STEP ""4a "'CIILOROPRENE (SOFT ORAIN. DU PONT TYPE AC NEOPRENE) The compositions resulting from steps A and B are 13 HEAT REACT[VE ALKYLPHENOLIC RESINS blended and admixed for a period Of 8 hours and gS 634NBAKEI-lTE-UNION then reduced IO the desired VlSCOSlty this i l'll5 (SP I74)(SCHENECTADY CHEM. CO) stance 52,000 centipoises) with a Solvent admixl0 HARB/rEK-IKMXSCHENECTADY CHEM C0.) lure compfisingl s HYDRATED CALCIUM SILICATE 40 percent Hexane 6% A'SBESTQS (CHOPPED FlBER) "'"MAONEsIUM OXIDE 30 percent Toluene 35 ZINC OXIDE 20 percent Methyl-ethylketone 0.5% PHENYL-ALPHA-NAPHTHYLAMINE 10 percent Acetone 0.5% NICKEL DlBUTYL DlTHlOCARBAMATE 0.5% DILAURYL THlODlPROPlONATE The final product is packaged into cartridges. a

EXAMPLE II EXAMPLE IV An adhesive composition having the following com- An adhesive composition having the following components was prepared following the procedure set forth ponents was prepared following the procedure set forth in Example I: V in Example I:

Parts by weight or 58 I DU PONT AD NEOPRENE (SOFT GRAlN) s PHENOLIC RESIN TYPE CKR No. I634 (BAKELITE)(UNION CARBlDE COMPANY) PHENOLIC RESIN, TYPE SP-l54 (SCHENECTADY CHEMICAL) 8 HYDRATED CALCIUM SILICATE 7 PHENOLlC RESIN, TYPE SP-l74 (SCHENECTADY CHEMICAL) 5 MAGNESIUM OXIDE 3 ZINC OXIDE 1.5% ASBESTOS FIBER 0.5% ANTIOxIDANT (PHENYL-ALPHA-NAPTHYLAMINE) 0.5% DILAURYL THlODlPROPlONATE 0.5% NICKEL DlBUTYL DlTHlOCARBAMATE TQTAL 10 Parts by Weight or Percent by Weight 54 DU PONT AD NEOPRENE (SOFT GRAIN) l0 PHENOLIC RESlN, TYPE CKR NO. 1634 (BAKELITE) (UNION CARBlDE COMPANY) 10 PHENOLlC RESIN, TYPE SP-l54 a HYDRATED CALClUM SILICATE EXAMPLE V 7 PHENOLIC REsIN. TYPE SP-l74 5 MAGNESIUM OXIDE An adhesive composition having the following comi igggg ponents was prepared by following the procedure set 0.5% ANTIOxIDANT forth in Example I:

(PHENYL-ALPHA- NAPTHYLAMlNE) A 55 05% DILAURYL Y THlODlPROPlONATE 0.5% NICKEL DIBUTYL DITHIOCARBAMATE Parts by Weight or Percent by Wgmhg DU PON'I- AD NEOPRENE (SOFT (BRAIN) 2 ag l g Comlnued The adhesives of Examples land H are also unique in y t V that they pass the Flame Penetration Tests as described ZlNC OXIDE ASBESTOS FIBER ANTIOXIDANT (PHENYLALPHA-NAPTHYLAMINE) DILAURYL THIODIPROPIONATE m7 is NlCKEL DlBUTYL DlTHlOCARBAMATE IQM The foregoing compositions were tested by Governin Forest Products Laboratory Fire Tests, Report No. ment certified laboratories by the procedures used by I443, revised September 1959 (Reafiirmed 1965) for the American Plywood Association Adhesives for 10 20 X 20inch plywood panels. These tests demonstrated Field-Gluing Plywood to Wood Framing (May 197l) that the adhesives were capable of withstanding the eleand FHA Bulletin UM-60. vatedtemperatures of the direct flame impingement The test samples were prepared in accordance with test. The test was terminated after 14-16 minutes due APA AFGl0. The following results were obtained: to plywood burning away prior to failure of the glue TABLE I line. The test showed glue line temperatures (thermocouple'registeredlof 430-5 F.

FHAAPA Go! All of the adhesives prepared in the specific examples TEST SHEAR STRENGTH Minimum standard used dry or essentially dry or anhydrous components Load inlounds jg and it has been found that the presence of water in the 4 admixture of component materials produces an inferior Wet Lumber 423 v 225 product. The test data indicates that the adhesive com- (31mm positions of the present invention have outstanding Frozen Lumber 806 150 I physical properties which permits their use in a variety M of applications including their use in building construc- Lumbe, 570 v 225 tions as a superior replacement for more traditional fas- (3-l -l C tening devices such as nails, staples, brads or the like.

i lin 16 338 so These adhesives may be employed under a variety of (Mel adverse circumstances such as in areas where fire resis- DURABIUTY TESTS tance is required, where low temperature application is encountered, where a variety of diverse materials are l to be bonded, where wet and frozen materials are to be Resistance I00% 90% (3-211) oined, and where the adhesive bond must have long Shear Smngm V227 225 life. The compositions described in the foregoing are fire-resistant adhesives whenapphed to wood or other A v objects and structures which are part of an element 395%? 100% which is subjected to a fire liability. One of the prob- I lems that is encountered in application, however, is Similar shear strength tests indicated superior results in that the solvents utilized are flammable materials and comparative tests with various commercial adhesives 40 that there is some flammability hazard in the applicanow on the market. The time delay factor indicates the tion. It has been found that this fire hazard in the appliaging of the adhesive from application 'to test. cation stage and immediately thereafter while the adhe- TABLE ll SHEAR LOADS (l m 4 tests) PRODUCT OF EXAMPLE COMPETlTlVE COMMERClAL agg- AGING 1 ii A B c o E 24 hrs. row 42*; 168 383 2% 418 F G H 72 m. 803 856 433 25s 276 26 days 2173 I008 100? The following data represents the results obtained from sive is drying may be sharply reduced or eliminated by shear tests of l X 4 inch white pine boards using the the employment of solvent systems which contain a composition of Example I with various aging times after fairly high percentage of non-flammable solvent mateapplication to the test date. A rials which are preferably essentially non-toxic or have TABLE m a low toxicity hazard. Solvents WhlCh suppress the flammability of other normally flammable materials such as hydrocarbon solvents or the like are preferred. Exem- DA OF AGING ftiii l0 Tnuls) plary of these materials are methylene chloride which i when used in a blend with hexane in a 40:60 ratio pro- 2 588 duces a non-flammable solvent for use in the composig' tions of the present invention. 7 1329 The adhesives are also characterized by good storage 28 I736 stability under a variety of hot and cold conditions. For

example, adhesives in gun-type cartridges may be shipped and stored at rather high temperature, such as encountered in a warehouse or on a truck, without thickening or gelling whereas conventional polychloroprene adhesives or cements display phasing in 30 to 90 days in storage or after application. The adhesives of the present invention on the other hand have a storage life of a year or more.

What is claimed is:

1. A process for preparing a fire resistant adhesive composition comprising on a weight percent basis: from 20 to 80 percent polychloroprene; from to 50 percent heat advancing, oil soluble phenolic resin of which at least percent is a resin which is thermally stable at 500F. and above; from 1 to 50 percent asbestos; from 2 to 20 percent of an oxide selected from the group consisting of magnesium and cadmium oxide; from 0 to 50 percent fillers; and from 0.1 to 2 percent each of a dialkyl thiodipropionate and a nickel dibutyl dithiocarbamate antioxidant, said process comprising:

A. Forming a mixture of the phenolic resin and a portion of the magnesium or cadmium oxide in an organic solvent, admixing the same until dispersion is complete, and permitting the admixture to prereact;

B. blending the polychloroprene elastomer with the remainder of the magnesium or cadmium oxides, the antioxidants, zinc oxide and asbestos fiber in a high shear mixing apparatus and then dissolving the blend in an organic solvent; and

C. blending the compositions obtained from Steps A and B at a temperature below about 140F. for a period of at least 8 hours.

2. A process according to claim 1 wherein the polychloroprene is employed in an amount of from 45 to 65 percent by weight of said composition.

3. A process according to claim 1 wherein the oxide is magnesium oxide and is employed in amounts of from 2 to 10 percent by weight.

4. A process according to claim 1 wherein the oxide employed is an admixture of magnesium and cadmium oxide in an aggregate amount of from 2 to 10 percent by weight.

5. A process according to claim 1 wherein from 30 to percent of the phenolic resin employed is a high cure rate resin having thermal stability at temperatures above about 500F.

6. A process according to claim 1 wherein the composition produced by Step C is admixed with solvents to a viscosity of from 23,000 to about 90,000 centipoises.

7. A process according to claim 1 wherein the antioxidants are dilauryl thiodipropionate and nickel dibutyl dithiocarbamate, each employed in an amount of from 0.1 to 2 percent by weight.

8. A process according to claim 1 wherein. Step C is carried out at a temperature below about F.

9. A process according to claim 1 wherein the composition of Step A is pre-reacted for a period of up to about 2 weeks.

UNITED. STATES PATENT OFFICE v v CERTIFICATE OF CORRECTION Patent No. 3,843,592 Dated October 22, 1974 Inventor(s) Garry R. Perkins It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the first page of the patent, in'the first column,

for the first patent listed under the heading "References Cited",' "12/1909" should be 12/1959 Column 1, line 10, delete Line 15, delete "2 Column 2, line 28, after "percent," insert preferably Column 3 line 52, delete "and", second"occu rrence Column 7, line 14, "AFG-lO" should be AFG-Ol Signed and sealed this 4th day of February 1975.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN I Attesting Officer Commissioner of Patents 

1. A PROCESS FOR PREPARING A FIRE RESISTANT ADHESIVE COMPOSITION COMPRISING ON A WEIGHT PERCENT BASIS: FROM 20 TO 80 PERCENT POLYCHLOROPRENE; FROM 15 TO 50 PERCENT HEAT ADVANCING, OIL SOLUBLE PHENOLIC RESIN OF WHICH AT LEAST 20 PERCENT IS A RESIN WHICH IS THERMALLY STABLE AT 500*F. AND ABOVE; FROM 1 TO 50 PERCENT ASBESTOS; FROM 2 TO 20 PERCENT OF AN OXIDE SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM AND CADMIUM OXIDE; FROM 0 TO 50 PERCENT FILLERS; AND FROM 0.1 TO 2 PERCENT EACH OF A DIALKYL THIODIPROPIONATE AND A NICKEL DIBUTYL DITHIOCARBAMATE ANTIOXIDANT, SAID PROCESS COMPRISING: A. FORMING A MIXTURE OF THE PHENOLIC RESIN AND A PORTION OF THE MAGNESIUM OR CADMIUM OXIDE IN AN ORGANIC SOLVENT, ADMIXING THE SAME UNTIL DISPERSION IS COMPLETE, AND PERMITTING THE ADMIXTURE TO PRE-REACT; B. BLENDING THE POLYCHLOROPRENE ELASTOMER WITH THE REMAINDER OF THE MAGNESIUM OR CADMIUM OXIDES, THE ANTIOXIDANTS, ZINC OXIDE AND ASBESTOS FIBER IN A HIGH SHEAR MIXING APPARATUS AND THEN DISSOLVING THE BLEND IN AN ORGANIC SOLVENT; AND C. BLENDING THE COMPOSITIONS OBTAINED FROM STEPS A AND B AT A TEMPERATURE BELOW ABOUT 140*F. FOR A PERIOD OF AT LEAST 8 HOURS.
 2. A process according to claim 1 wherein the polychloroprene is employed in an amount of from 45 to 65 percent by weight of said composition.
 3. A process according to claim 1 wherein the oxide is magnesium oxide and is employed in amounts of from 2 to 10 percent by weight.
 4. A process according to claim 1 wherein the oxide employed is an admixture of magnesium and cadmium oxide in an aggregate amount of from 2 to 10 percent by weight.
 5. A process according to claim 1 wherein from 30 to 100 percent of the phenolic resin employed is a high cure rate resin having thermal stability at temperatures above about 500*F.
 6. A process according to claim 1 wherein the composition produced by Step C is admixed with solvents to a viscosity of from 23,000 to about 90,000 centipoises.
 7. A process according to claim 1 wherein the antioxidants are dilauryl thiodipropionate and nickel dibutyl dithiocarbamate, each employed in an amount of from 0.1 to 2 percent by weight.
 8. A process according to claim 1 wherein Step C is carried out at a temperature below about 120*F.
 9. A process according to claim 1 wherein the composition of Step A is pre-reacted for a period of up to about 2 weeks. 